JP6418898B2 - Piezoelectric generator - Google Patents

Description

  The present invention relates to a piezoelectric power generator.

  Conventionally, piezoelectric power generation devices using piezoelectric elements are known. For example, there is known a piezoelectric power generation device that includes a structure in which a power generation unit in which a piezoelectric body and a metal plate (vibration plate) are joined is supported by a support, and converts vibration energy into electric energy (for example, Patent Documents). 1 and 2).

JP 2006-032935 A JP 2013-135596 A

  The piezoelectric power generation apparatus has a problem that the amount of power generation in the vibration region on the low frequency side is low because the resonance frequency appears in the vibration region on the high frequency side due to downsizing. In this technical field, it is particularly demanded to reduce the size of the apparatus and improve the power generation efficiency.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a small piezoelectric power generator that can improve the amount of power generation in a vibration region on the low frequency side.

The piezoelectric power generation device of the present invention includes a piezoelectric element that is a power generation unit and a diaphragm, a power generation unit in which the piezoelectric element is joined to the diaphragm, and a first support that supports the diaphragm. a piezoelectric power generator wherein the diaphragm is extended region between said piezoelectric element to said first support, on one side of the direction perpendicular to the mounting surface for mounting the piezoelectric element And a bent portion bent so as to protrude toward the mounting surface and a bent portion bent toward the other side in a direction perpendicular to the mounting surface .

  According to the piezoelectric power generation device of the present invention, the amount of power generation in the vibration region on the low frequency side can be improved.

(A) is a schematic perspective view which shows an example of the piezoelectric power generator of this embodiment, (b) is a schematic sectional drawing of the piezoelectric power generator shown to (a). It is a schematic sectional drawing which shows the other example of the piezoelectric power generator of this embodiment. It is a schematic sectional drawing which shows the other example of the piezoelectric power generator of this embodiment. It is a schematic sectional drawing which shows the other example of the piezoelectric power generator of this embodiment. (A) is a schematic perspective view which shows an example of the piezoelectric power generator of this embodiment, (b) is a schematic sectional drawing of the piezoelectric power generator shown to (a). It is a schematic sectional drawing which shows the other example of the piezoelectric power generator of this embodiment. It is a schematic sectional drawing which shows the other example of the piezoelectric power generator of this embodiment. It is a schematic sectional drawing which shows the other example of the piezoelectric power generator of this embodiment.

  Hereinafter, an example of the piezoelectric power generation apparatus of the present embodiment will be described in detail with reference to the accompanying drawings. In addition, this invention is not limited by embodiment shown below.

  FIG. 1A is a schematic perspective view illustrating an example of the piezoelectric power generation device of the present embodiment, and FIG. 1B is a schematic cross-sectional view of the piezoelectric power generation device of FIG. The piezoelectric power generation apparatus of this embodiment shown in FIG. 1 includes a piezoelectric element 11 that is a power generation unit and a diaphragm 12, and a power generation unit 1 in which the piezoelectric element 11 is joined to the diaphragm 12, and the diaphragm. 1 is a piezoelectric power generation apparatus including a first support body 21 that supports a piezoelectric element 12. The diaphragm 12 includes a piezoelectric element 11 in an extension region between the piezoelectric element 11 and the first support body 21. The bent portion 13 is bent so as to protrude toward at least one side in a direction perpendicular to the mounting surface 122.

  The piezoelectric power generation apparatus according to the present embodiment includes a piezoelectric element 11 that is a power generation unit and a diaphragm 12, and includes a power generation unit 1 in which the piezoelectric element 11 is joined to the diaphragm 12.

The piezoelectric element 11 constituting the power generation unit 1 is composed of a piezoelectric body having piezoelectricity and electrodes provided on both main surfaces thereof, and converts vibration energy transmitted from the diaphragm 12 into electric energy. It is. Examples of piezoelectric materials having piezoelectricity include lead zirconate titanate, lead titanate, lithium niobate, lithium tantalate, Bi layered compounds, tungsten bronze structure compounds, etc. Piezoelectric ceramics, piezoelectric resin, etc. can be used. Moreover, silver etc. can be used suitably as an electrode material. Although not shown, the electrodes of the piezoelectric element 11 are electrically connected to an external circuit through wiring connected thereto. Further, the piezoelectric element 11 shown in FIG. 1 has a rectangular plate shape, but may have a disk shape or the like.

A piezoelectric element 11 is bonded to the diaphragm 12 constituting the power generation unit 1 using a resin adhesive such as epoxy or acrylic, and vibration energy generated in the diaphragm 12 is transmitted to the piezoelectric element 11. The diaphragm 12 is formed of a material that is easily elastically deformed and easily bent, and that does not easily break even when plastically deformed during an overload, and has a thickness of, for example, 0.05 mm to 0.5 mm. Examples of such materials include metallic materials such as phosphor bronze, brass, white, Corson alloy, and stainless steel (SUS). By using these, the elastic deformation region of the diaphragm 12 can be widened, and the fatigue fracture resistance against repeated stress is increased, so that the durability can be improved. Here, the vibration plate (metal plate) made of a metal material can be formed by press punching or etching. In particular, by using a conductor such as a metal plate as the diaphragm 12, it can also be used as a wiring for connecting to an external circuit. Furthermore, it can also serve as the electrode of the piezoelectric element 11. In view of weight reduction and processing difficulty, a resin plate such as acrylic may be used. Further, the diaphragm 12 shown in FIG. 1 has a rectangular plate shape in plan view, which has a region where the piezoelectric element 11 is mounted and an extension region 121 between the piezoelectric element 11 and the first support. However, it may be disk-shaped.

  The power generation unit 1 is supported by a pair of first support bodies 21 so as to vibrate. Specifically, the entire power generation unit 1 is supported by the pair of first support bodies 21 via extension regions 121 extending between the pair of first support bodies 21 from both sides of the piezoelectric element 11 in the diaphragm 12. ing. Here, the first support 21 supports the end portion of the diaphragm 12, and the supported portion serves as a fulcrum when the diaphragm 12 is bent. Therefore, the first support 21 is not easily damaged, and in addition, since the vibration of the diaphragm 12 is not attenuated, it is necessary to suppress elastic deformation. Generally, a resin such as ABS resin or polypropylene having excellent hardness, or a metal such as stainless steel (SUS), phosphor bronze, or brass is used. When the 1st support body 21 consists of resin, it shape | molds in the state which hold | maintained the electric power generation unit 1. FIG. When a metal is used as the first support 21, an insulator may be interposed on the contact surface with the diaphragm 12 in order to avoid conduction with the diaphragm 12.

  The extension region 121 of the diaphragm 12 is at least one side (upward or downward) of a direction perpendicular to a mounting surface 122 (hereinafter, simply referred to as a mounting surface 122) on which the piezoelectric element 11 is mounted. It has a bent portion 13 that is bent so as to protrude downward.

  Specifically, in FIG. 1, the extension region 121 of the diaphragm 12 has a bent portion 13 that is bent in a direction perpendicular to the mounting surface 122 (upward) and folded in the middle. An example is shown in which it is bent again from a direction perpendicular to the mounting surface 122 toward a parallel direction. In addition, it extends in a direction parallel to the mounting surface 122 on the outer side, reaches the first support body 21 disposed on the outer side, and is supported by the first support body 21.

  When the diaphragm 12 is made of metal, the bent portion 13 can be formed by pressing. In the case where the diaphragm 12 is made of resin, the bent portion 13 can be formed by injection molding using a mold having the shape of the bent portion 13.

  Here, the increase in the output voltage depends on the resonance frequency of the power generation unit 1. When the power generation unit 1 of the size is manufactured and both ends of the diaphragm 12 are held by the first support 21, the resonance frequency is approximately in the vicinity of 2.5 kHz, although it varies greatly depending on the material. However, generally, external applied vibration for performing vibration power generation is often 500 Hz or less. Since the electromotive force of the power generation unit 1 is due to the displacement of the power generation unit 1 itself, the amount of displacement increases when the resonance frequency of the power generation unit 1 approaches the vibration frequency, and as a result, the output voltage can be increased.

  That is, by adopting the configuration as in this embodiment, the effective length of the diaphragm 12 can be increased while maintaining the miniaturization of the piezoelectric power generation device, the resonance frequency is lowered, and the frequency range in which it is used is reduced. Impedance can be reduced. Therefore, by reducing the output impedance of the diaphragm 12 and approaching the input impedance of the load, the matching loss is reduced, so that a high power generation amount can be obtained in the vibration region on the low frequency side. Further, the vibration durability can be improved by the stress relaxation effect of the bent portion 13.

  In addition, as a shape of the bending part 13, for example, it is preferable that the bending radius is three times or more the thickness of the diaphragm 12 in terms of improving the power generation amount despite being small. Similarly, it is effective that the distance (height) from the position of the mounting surface 122 to the bent portion 13 is not less than three times the thickness of the diaphragm 12.

  Here, as shown in FIG. 2, the extension region 121 has a bent portion 131 bent so as to protrude toward one side (upward) in a direction perpendicular to the mounting surface 122 and a direction perpendicular to the mounting surface 122. It is more preferable to have a bent portion 132 that is bent so as to protrude toward the other side (downward). Specifically, in FIG. 2, in the extension region 121 of the diaphragm 12, the bent portion is bent from the direction parallel to the mounting surface 122 toward the vertical direction (downward direction) and folded back halfway. 132, and a bent portion 131 formed so as to be folded after extending in a direction (upward) perpendicular to the mounting surface 122, and thereafter, from a direction perpendicular to the mounting surface 122 to a direction parallel to the mounting surface 122 And bends. It should be noted that the outside of the bent portion 131 extends in a direction parallel to the mounting surface 122 (the left-right direction in the figure), reaches the first support body 21 disposed on the outside, and reaches the first support body 21. It is supported. By setting it as such a structure, since the displacement of the diaphragm 12 becomes larger, electric power generation amount can be improved further.

Further, as shown in FIG. 3, a first stopper 14 that is provided in the vicinity of the bent portions 131 and 132 and restricts the amount of displacement of the bent portions 131 and 132 may be provided. The first stopper 14 is provided on the upper side of the bent portion 131 and the lower side of the bent portion 132 so as to have a predetermined interval (an interval enough to suppress excessive displacement in a direction (vertical direction) perpendicular to the mounting surface 122). With the first stopper 14, the bending portions 131 and 132 of the vibration plate 12 have the first stop when the excessive displacement in the direction perpendicular to the mounting surface 122 (vertical direction) is about to occur. Since the excessive displacement of the stopper 14 is suppressed, damage to the piezoelectric power generation device when excessive vibration occurs can be suppressed and durability can be improved. In the configuration shown in FIG. 3, the first stopper 14 is formed integrally with the first support 21. However, any configuration that restricts excessive displacement of the bent portions 131 and 132 may be used. The stopper 14 may be formed separately from the first support 21 and fixed to the first support 21. In addition, the space | interval of the grade which suppresses said excessive displacement is suitably determined in the range of 0.005-1.0 mm according to the magnitude | size of a piezoelectric generator, for example.

  Furthermore, as shown in FIG. 4, the first stopper 14 may have a concave portion 141 into which the bent portions 131 and 132 enter. In order to restrict displacement in a direction parallel to the mounting surface 122, the concave portion 141 has a predetermined interval (irregularity in a direction parallel to the mounting surface 122) inside and outside the bent portion 131 and inside and outside the bent portion 132. It is provided so as to have an interval enough to suppress excessive displacement. With such a configuration, even if an irregular excessive displacement that is not assumed in a direction parallel to the mounting surface 122 is generated, the bent portions 131 and 132 of the diaphragm 12 are formed on the first stopper 14. Since it hits the formed recess 141, irregular displacement in a direction parallel to the mounting surface 122 is suppressed, so that durability when abnormal vibration occurs can be improved. In addition, the space | interval of the grade which suppresses said excessive displacement is suitably determined in the range of 0.005-1.0 mm according to the magnitude | size of a piezoelectric generator, for example.

  Further, as shown in FIG. 5, several power generation units 1 are arranged in a direction perpendicular to the mounting surface 122, and the first support 21 may integrally support a plurality of power generation units 1. . In this case, it is preferable that the piezoelectric elements 11 of the respective power generation units 1 are arranged so as to overlap each other in plan perspective. With such a configuration, the voltage can be increased when a plurality of piezoelectric elements 11 are connected in series, while the current can be increased when a plurality of piezoelectric elements 11 are connected in parallel, thereby further increasing the amount of power generation.

  In this case, the height from the position of the mounting surface 122 to the bent portion 13 (the bent portions 131 and 132 bent toward the one main surface side (upper side) and the other main surface side (lower side) of the mounting surface 122 are provided. In some cases, the sum of the respective heights) is, for example, 90% or less of the interval between the adjacent diaphragms 12.

  Further, as shown in the figure, when the extension region 121 of each diaphragm 12 has a bent portion 13 bent so as to protrude toward the one side from the mounting surface 122, each displacement amount May be provided, and each of the first stoppers 14 may have a recess 141 into which the bent portion 13 enters.

  Further, as shown in FIG. 6, the first support body 21 that integrally supports the plurality of power generation units 1 from the outer edge side, and the plurality of power generation units 1 are respectively integrated in the region inside the piezoelectric element 11. You may provide the movable 2nd support body 22 to support.

Here, for example, through holes are respectively formed in the plurality of piezoelectric elements 11 and the plurality of diaphragms 12, and the second support body 22 is provided so as to pass through these through holes. Specifically, the second support 22 sandwiches the piezoelectric elements 11 and the diaphragms 12 with the rod-shaped portions 221 inserted through the through holes of the plurality of piezoelectric elements 11 and the diaphragms 12. And a support portion 222 to support. Here, the rod-shaped portion 221 and the support portion 222 may be formed in a bolt shape and a nut shape, or may be bonded and fixed to each other. These may be formed of resin in the sense of preventing short circuit of each power generation unit 1, and metal after preventing short circuit of each power generation unit 1 by providing an interval or interposing an insulator. May be formed.

  In addition, after fixing the several electric power generation unit 1 with the 2nd support body 22, the 1st support body 21 is integrally shape | molded on each outer edge side of the several electric power generation unit 1, FIG. The form shown can be easily produced.

  By setting it as such a structure, the displacement direction of all the diaphragms 12 can be synchronized. For this reason, the generated potential is always in the same phase and does not cancel each other, so that loss during power generation can be reduced.

  Furthermore, as shown in FIG. 7, a second stopper 15 that is provided in the vicinity of the second support 22 and restricts the amount of displacement of the second support 22 may be provided. The second stopper 15 is provided on the upper side of the upper end of the second support 22 so as to have a predetermined interval (an interval enough to suppress excessive displacement in a direction (vertical direction) perpendicular to the mounting surface 122). When the second stopper 15 is present, all the diaphragms 12 including the second support 22 are about to be excessively displaced in the direction perpendicular to the mounting surface 122 (up and down direction). Since the excessive displacement of the upper end of the second support 22 is suppressed by the second stopper 15, the piezoelectric power generation device can be prevented from being damaged when excessive vibration occurs, thereby improving durability. In the configuration shown in FIG. 7, the second stopper 15 is formed integrally with the first support 21, but the second stopper 15 is formed separately from the first support 21, It may be fixed to the first support 21. Further, the interval enough to suppress the excessive displacement is appropriately determined within a range of, for example, 0.005 to 1.0 mm according to the size of the piezoelectric power generation device.

  Here, as shown in FIG. 8, the second stopper 15 may have a recess 151 into which the second support 22 enters. The recess 151 has a predetermined interval (mounting surface) on the inner side and outer side of the upper end portion 221 of the second supporting member 22 in order to restrict the second supporting member 22 from being displaced in a direction parallel to the mounting surface 122. 122 is provided so as to have an interval sufficient to suppress irregular excessive displacement in a direction parallel to 122. By adopting such a configuration, even if an irregular excessive displacement occurs in a direction parallel to the mounting surface 122, the second support 22 hits the recess 151 formed in the second stopper 15. Since irregular displacement in a direction parallel to the surface 122 is suppressed, durability when abnormal vibration occurs can be improved. In addition, the space | interval of the grade which suppresses said excessive displacement is suitably determined in the range of 0.005-1.0 mm according to the magnitude | size of a piezoelectric generator, for example.

  Next, a specific example of the piezoelectric power generation device of this embodiment will be described.

  The piezoelectric element has a configuration including a rectangular plate-shaped piezoelectric ceramic having a length of 8 mm, a width of 8 mm, and a thickness of 0.1 mm, and electrodes made of a conductor mainly composed of silver on both main surfaces thereof. . The vibration plate is a metal plate made of phosphor bronze having a length of 18 mm, a width of 10 mm, and a thickness of 0.1 mm, and is bent in a direction perpendicular to the main surface and having a height of 3 mm and a bent portion having the shape shown in FIG. Formed. The piezoelectric element and the diaphragm were bonded with an acrylic adhesive. The first support was made of an epoxy resin having a height of 6 mm.

  The open output voltage in the no-load state of the piezoelectric power generation apparatus according to the present example manufactured as described above was measured. When a vibration with a frequency of 100 Hz and an acceleration of 1 G was applied, a voltage of 0.64 V was observed.

On the other hand, as a comparative example, a voltage increase of 12% was observed as compared with the output voltage of 0.57 V of the power generation device having the same outer dimensions and the bent portion not formed on the diaphragm.

  In addition to the shape perpendicular to the mounting surface of the piezoelectric generator, a bent portion is provided at a height of 3 mm on the other side in the direction perpendicular to the mounting surface as shown in FIG. The measurement of the open output voltage in the no-load state was further improved to 0.70 V when vibration with a frequency of 100 Hz and an acceleration of 1 G was applied.

  From the above results, it was confirmed that the power generation amount in the low frequency region can be improved in the configuration of this example.

DESCRIPTION OF SYMBOLS 1 Power generation part 11 Piezoelectric element 12 Diaphragm 121 Extension area | region 13, 131, 132 Bending part 14 1st stopper 141 Recessed part 15 2nd stopper 151 Recessed part 21 1st support body 22 2nd support body 221 Rod-shaped part 222 Supporting part

Claims (9)

A piezoelectric power generation apparatus including a piezoelectric element that is a power generation unit and a vibration plate, a power generation unit in which the piezoelectric element is bonded to the vibration plate, and a first support that supports the vibration plate. Te, the diaphragm is extended region between said piezoelectric element to said first support, bent so as to protrude toward the one side in the direction perpendicular to the mounting surface for mounting the piezoelectric element A piezoelectric power generation device comprising a bent portion and a bent portion bent so as to protrude toward the other side in a direction perpendicular to the mounting surface . The piezoelectric power generation device according to claim 1, wherein each of the bent portions is a curved surface .   The piezoelectric power generator according to claim 1, wherein the diaphragm is made of a metal material.   4. The piezoelectric power generation device according to claim 1, further comprising a first stopper that is provided in the vicinity of the bent portion and regulates a displacement amount of the bent portion. 5. .   The piezoelectric power generator according to claim 4, wherein the first stopper has a concave portion into which the bent portion enters.   The plurality of power generation units are arranged in a direction perpendicular to the mounting surface, and the first support body integrally supports the plurality of power generation units. 5. The piezoelectric power generation device according to claim 5.   The first support body that integrally supports a plurality of the power generation units from the outer edge side, and the movable second support that integrally supports the plurality of power generation units in a region inside the piezoelectric element, respectively. The piezoelectric power generation device according to claim 6, further comprising a body.   The piezoelectric power generation device according to claim 7, further comprising a second stopper that is provided in the vicinity of the second support body and regulates a displacement amount of the second support body.   The piezoelectric power generation device according to claim 8, wherein the second stopper has a concave portion into which the second support body enters.

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